1. Field of the Invention
The present invention relates to a method and apparatus for threading acrylic filaments on rollers of an oxidizing furnace used in the oxidizing stage of the production of carbon fibers from the acrylic filaments.
2. Description of the Prior Art
It is well known to produce carbon fibers from acrylic filaments by submitting the acrylic filaments to an oxidizing treatment and then to a carbonizing treatment. It is also known from Japanese Patent Publication No. SHO 51-27778 or SHO 52-74026 to execute the oxidizing treatment in an oxidizing furnace with multistage rollers. The furnace with multistage rollers, which is a comparatively small furnace providing a relatively long oxidizing zone, is just beginning to be used as an oxidizing furnace for the acrylic filaments. However, this furnace takes a relatively long time for the oxidizing treatment.
In this type of furnace with multistage rollers the filaments have to be threaded in a zigzag manner on a plurality of rollers. In the conventional method of threading filaments on rollers, the filaments were manually threaded successively on a plurality of rollers and the work was extremely bothersome. Another trouble in the conventional method of threading filaments on rollers was that when the temperature of the atmosphere in the furnace was raised to the oxidizing treatment temperature after the filaments were threaded, the filaments were sometimes broken or slackened on account of contraction or expansion and thereby the start of normal operation for oxidizing treatment was hindered.
Meanwhile Japanese Patent Publication No. SHO 54-1811 discloses a method for threading filaments by means of a chain, in which a filament-fastening bar is installed between a pair of chains provided at the both ends of rollers. The filaments are fastened to this bar and when the chains are moved, the filaments are threaded on said rollers.
When this method was applied to the furnace with multistage rollers, acrylic filaments having a specific treating hysteresis suffered heavy contraction in the atmosphere of 180.degree. C. to the oxidizing treatment temperature in the furnace, resulting in a failure of filament-threading by the chains. In light of this experience, it was also tried to employ less contracting lead filaments in the hot atmosphere of the furnace, but this was equally bothersome and could not be employed from the view point of practical application. Nevertheless the merit of threading the filaments in an atmosphere of 180.degree. C. to the oxidizing treatment temperature was fully appreciated, because unlike in the conventional method of threading the filaments at a room temperature and then elevating the furnace temperature for normal operation, breakage of filaments would be reduced and the time taken to elevate the temperature of the atmosphere from a room temperature to the heat-treatment temperature would be drastically cut back, thereby resulting in an increased productivity. Thus the demand for realizing this new threading art has been mounting.